This invention relates to an improved separation of a multi-component mixture containing a noncondensible (under ordinary temperature and pressure) component and at least one condensible (under ordinary temperature and pressure) component. In particular, it relates to the separation utilizing fractional distillation.
In chemical processes, it is often necessary to separate a mixture containing noncondensible and condensible components. "Condensible" throughout this specification shall mean capable of being condensed under normally available plant conditions. An example of a mixture which can be separated using the method of the present invention is a mixture of hydrogen, propylene and ethylene. Such mixture has to be separated, for example, in a process of copolymerization of propylene and ethylene. In that process, it is desirable to use in the reaction zone small amounts of hydrogen. The presence of hydrogen in a narrowly defined concentration leads to an improved catalyst productivity and allows improved control of flexural modulus of a copolymer produced in the reaction. In most copolymerization processes, unreacted ethylene and propylene are separated from the copolymer and each other and recycled to the reaction zone. Some of the hydrogen is dissipated in the process; consequently, in order to maintain a narrowly defined concentration thereof in the reaction zone it is necessary to remove all hydrogen from the reagents recycled to the reaction zone and monitor the concentration of hydrogen by introduction of fresh carefully measured amount of hydrogen with each batch, or at a predetermined rate in a continuous process. Different methods of removal of hydrogen from recycle monomer stream are disclosed, for example, in U.S. Pat. Nos. 3,644,583 and 2,900,326.
The present invention provides an improved method for separation of a stream containing at least one of each condensible and noncondensible components.
Thus, one object of this invention is to provide an improved process for separation of a stream containing at least one condensible and one noncondensible component.
Another object of the invention is to provide for an efficient separation of a stream containing hydrogen, propylene and ethylene.
Still another object of the invention is to provide an improved process for catalytic copolymerization of ethylene and propylene in the presence of hydrogen.
A further object of the invention is to provide a method for the removal of hydrogen from an unreacted propylene-ethylene monomer stream and separation of said monomers, which uses a minimum amount of energy and equipment.
A still further object of the invention is to provide a method for separation of hydrogen, unreacted propylene and unreacted ethylene, which eliminates the need for an overhead condenser or any other heat exchanger in the fractionation column used for separation of hydrogen from ethylene.
Other objects of the invention will become apparent to those skilled in the art upon studying this disclosure.